The management of power consumption within microprocessors is becoming increasingly crucial for a number of reasons. As operating frequencies and circuit densities have increased, heat generation within microprocessors has also increased to the extent that thermal considerations are a limiting factor in integrated circuit (IC) design and manufacture. Specifically, the dissipation of heat generated by a microprocessor is a design constraint in both portable and desktop computers. In desktop computers, the dissipation of heat has serious cost implications since a cooling apparatus is typically required to support the microprocessor. In portable computers, in addition to increased costs due to cooling apparatus, the problem of cooling a microprocessor is exacerbated by the space limitations within which such cooling apparatus can be installed. Indeed, the operating frequency of a microprocessor that can be installed within a portable computer may be determined, and limited, by the ability of associated cooling apparatus adequately to cool the microprocessor. Accordingly, the reduction of heat generated by a microprocessor is highly desirable.
Further, the proliferation of portable computers, which must often rely on self-contained batteries for power, has also led to increasing attention being given to reducing power consumption within such portable computers. Power management efforts in the field of portable computing have focused on extending the time a portable computer can operate while drawing power from a charged battery. The minimization of power consumption and heat generation within a microprocessor of a portable computer is also particularly desirable for a number of reasons. Increased battery life results from less power being consumed by both the microprocessor and cooling devices employed in computers to cool the microprocessor, such as fans. Decreased heat generation within the microprocessor also allows processors having higher operating frequencies to be installed in portable computers. Decreased heat generation also allows for a reduction in the size, or even the elimination, of cooling apparatus associated with a microprocessor, thus facilitating more compact portable computers.
Accordingly, there is a need to reduce both the power consumption, and specially the accompanying heat generation, within integrated circuits in general, and within microprocessors in specific.